1. Field of the Invention
The present invention relates to an apparatus and method for handling substrates in a processing system and more particularly to a contact cup flexibly disposed on a substrate support blade.
2. Background of the Related Art
The advantages of using automated substrate handling devices, or robots, in the fabrication of integrated circuits to transfer substrates such as silicon wafers throughout a processing system are well established. Typically, cassettes containing substrates are moved through a semiconductor fabrication facility and delivered to various processing systems. One or more robots are located in a central transfer region and are capable of linear and/or rotational movement to retrieve substrates from the cassettes, shuttle them between various processing chambers within a multichamber processing system, and ultimately replace the processed substrates into the cassettes for removal from the system.
In many processing systems, substrates are processed in a face-up position, that is, with the processing surface of the substrate in a face-up position. Substrates are stored in cassettes, retrieved and shuttled between processing chambers, and finally replaced into the cassette while in a face-up position. A robot blade disposed at a distal end of a robot arm is positioned underneath the substrate to lift and transport the substrate within a system.
However, modem trends in semiconductor fabrication have led to processing systems wherein substrates are processed in a face-down position. For example, as feature sizes decrease and copper becomes a metal of choice, there is a trend to use electroplating systems to form metallized features on a substrate. Current designs of electroplating systems require face-down processing of substrates in electroplating cells. As a result, there is a need to flip substrates to a face-down position for processing in electroplating cells. After processing, substrates need to be flipped back to a face-up position for transfer to other processing cells and for replacement into substrate cassettes, etc.
To accomplish flipping of a substrate, the substrate is typically secured to the end portion of the robot arm, known as a blade, by vacuum chucking, which uses a vacuum to secure the substrate to a contact cup disposed blade. The blade has a contact cup disposed at a point of contact with the substrate. In vacuum chucking, a vacuum is applied to the volume defined between the contact cup and the substrate. The vacuum is sufficient to secure the substrate to the contact cup. After the substrate is vacuum chucked to the blade and removed from the cassette, the blade flips the substrate and positions the substrate face-down for delivery into an electroplating processing cell. After processing, the robot blade is positioned above the substrate and then lowered until the blade contacts the backside surface of the substrate. The process of attaching and retrieving a substrate that is in an inverted position is known as an inverted hand-off. The substrate is then vacuum chucked to the blade via the contact cup, lifted out of the processing cell, and again flipped for further face-up processing.
One problem encountered in transferring substrates within a processing system is that it is difficult to align the contact cup of the blade with the substrate when the substrate is in a face-down position so that the substrate can be vacuum chucked to the blade and lifted from the processing cell. Various factors can lead to inaccurate alignment between the blade and the substrate in complex processing systems, such as those used in semiconductor fabrication systems, including unreliable calibration of the robot and uncertainties as to station locations due to thermal expansion, etc. within the processing system. When substrates are transferred in a face-up position, as in typical traditional processing systems, the blade is positioned underneath the substrate so that gravity helps assure flush contact between the contact cup and a substrate. However, during an inverted handoff, where the blade is positioned above a face-down substrate, proper alignment for a sealed engagement between the contact cup and the substrate backside surface is more difficult to achieve. Accurate alignment is especially important in an inverted handoff to provide a good vacuum seal between the blade and the substrate for reliable vacuum chucking to enable the substrate to be lifted by the blade. Inaccurate alignment during an inverted hand-off can result in failed hand-offs, damaged substrates and reduced system throughput.
Therefore, there is a need for a robot that can reliably secure a substrate to a blade thereof.
The invention generally provides a robot blade for handling substrates in a processing system. In one aspect, a robot blade of the invention includes a contact cup is flexibly attached thereto to compensate for inaccurate alignment of the blade with a substrate and allow the contact cup to align with and come into flush contact with the substrate. This allows the substrate to be reliably secured to the blade when retrieved from a face-down position when the blade is positioned above the substrate.
In another aspect of the invention, a method of handling a substrate is provided, wherein the contact cup flexibly attached to the substrate support blade that contacts the substrate. The blade is lowered so that the contact surface of the contact cup contacts the backside of the face-down substrate and then the contact cup is vacuum chucked to the substrate via a vacuum created behind the backside of a substrate. As the contact sup comes into contact with the substrate, the contact cup deforms such that the entire contact surface contacts the substrate backside.